"#1. I have always added my first hopping after I have gotten the hot break to be skimmed off..."

Whether you knew it or not, adding the hops after a vigourous boil is attained is what is now practiced in all German professional breweries. It turns out that the albumin (that white scum) entrains hop constituants if it is present. This results in lower hop utilization and a reduction in head retention. In prior German studies, the practice of first wort hopping was thought to impart a "smoother" bitterness. What they did not take into account that this perception was due to a decreased alpha/beta utilization and loss of myrcene, cohumulone and other essentials in the albumin, not the supposed "more gentle extraction." They didn't even measure any other effects... such as head loss! Hard to imagine they made such a bad recommendation given the anal, engineering/quality based beer industry that exists in Germany! The current recommendation is that hops never be added before 10 minutes of VIGOROUS rolling boil has occured.

"... addition after a vigorous boil and that starts my 60 minute boil time schedule (and reduces the chance of a boilover)."

A 60 minute boil is ok with extract only batches, but for partials/steeps and all-grain, 90 minutes will maximize protein break (assuming the right boil pH). Ensuring this occurs will be worth the extra 30 minutes as it will greatly reduce the conditioning time of your beer, particularly if they are lagers. After all, you want to drink em' faster don't ya?

"#2. I have found that even with fully modified malts, a feable attempt at a protein rest will result in clearer beer but clear beer is not my main objective, but nice. "

What experience & education has taught me is that six proceedural mistakes (or combinations of them) lead to hazes (other than bacterial, dry hop or yeast induced):

1) Not vorlaufing (recirculating) grain runoffs until COMPLETELY clear with NO grain/husk/stach presence.

4) Poor primary to secondary to tertiary transfer timing and management. Yes... 2 stages of fermentation, 1 stage of settling. ( I've elaborated on this technique before on this forum, but if you want details on this and why, request it and I'll post.)

5) Inadequate conditioning time.

"#3. I've always suspected that the cooled wort needed a bit of aeration but that the yeast was needing oxygen more so & when doing a starter I always splash the starter to aerate. "

Yes... the yeast need the oxgen, not the wort. If possible, start using a fish pump with an airstone attached to a sterile air filter. Aerate for at least 1 hour and you'll be a believer. I'm using this technique in my brewery (albeit scaled up... my average pitching slurry volume is 5 gallons for ales and 12 gallons for lagers) and at 68 deg. f. my ales ferment to terminal gravity within 5 days and at 49 deg. F. my lagers ferment terminal within 10 days. But, in actuality, I pitch based on viability X cell density, not liquid volume, so those figures are estimates of slurry volumes and can vary somewhat.

An aside... if you use dry yeast, con't aerate at all. They only need hydrated at around 90 degrees for 30 minutes prior to use. Put in the water without stirring for 15 then stir the yeast in and let it settle for another 15. The reason that this is all that is needed is that it takes this long for the yeast to even wake up. And when they do, they need a ton of water to re-expand their cellular walls and functions. During this period, they are not able to uptake oxygen. Besides, if processed by a quality yeast producer, the yeast was dried at the peak of it's vitality when it had a surplus of enzymes. This is not how we receive liquid cultures... they have undergone glycolosis in preparation for dormancy. This is why oxygen/air is recommended. The yeast need it to re-build their cell walls to enter the reproduction phase where they bud. But, any more oxgen has a negative effect on fermentation and ester formation. This is why I recommend using AIR not oygen. It is impossible to get too much oxgen in a starter using air but it is very easy to do so with pure oxygen. If too much oxygen is present in a starter or wort, the media will become toxic to the yeast and will result in substantial yeast death.

Looks like I can improve with using some of your advice. I see I need to boil longer. And recirculate a bit longer too.

I appreciate your taking the time to elaborate on this. I am not a newbie but am an avid Hobbyist Homebrewer doing all-grain, just looking to improve with education. OK, maybe some better equipment too! I am drinking one of the best beers I have ever tasted right now... Could be a little clearer though. My APA House Favorite.

Yes, as I stated, it is best to only aerate the starter if you are so equipped to do this. The reason is that once the yeast has all the oxygen it needs to build strong cell walls and reproduce, it does not need any more. Any additional oxygen beyond that point will cause them to stay in a reproductive state rather than begin a fermentative state.

Just to clarify, do you mean
a) they will continue to absorb oxygen and produce lipids for their cell walls while reproducing AERObically (no fermentation)

or do you mean

b) they will continue to absorb oxygen and produce lipids for their cell walls
while reproducing anaerobically (with fermentation)

if its a), doesn't this go against all previous knowledge and experience regarding the crabtree effect which causes anaerobic fermenation even in the presence of oxygen?

a) they will continue to absorb oxygen and produce lipids for their cell walls while reproducing AERObically (no fermentation)

Not exactly... their aerobic phase is actually a lag phase before reproduction phase. They take in oxygen THEN they begin reproduction which, if there was not an excess of oxygen, begins the anaerobic phases.

or do you mean:

b) they will continue to absorb oxygen and produce lipids for their cell walls
while reproducing anaerobically (with fermentation)

No... they will only absorb enough oxygen oxygen to begin wall building.

if its a), doesn't this go against all previous knowledge and experience regarding the crabtree effect which causes anaerobic fermenation even in the presence of oxygen?

If you delivered the correct amount of oxygen to the starter, there will be no oxygen left in solution within 20 minutes. This assumes good yeast health, of course! I routinely measured this occurance while studing brewing microbiology at Siebel. It is a great indicator of yeast vitality.

Once budding has begun, there will be a small amount of fermentation going on, but the wort should be anaerobic at this point. Until critical population is reached and they stop reproducing, logarithmic fermentation will not begin.

a) they will continue to absorb oxygen and produce lipids for their cell walls while reproducing AERObically (no fermentation)

Not exactly... their aerobic phase is actually a lag phase before reproduction phase. They take in oxygen THEN they begin reproduction which, if there was not an excess of oxygen, begins the anaerobic phases.

or do you mean:

b) they will continue to absorb oxygen and produce lipids for their cell walls
while reproducing anaerobically (with fermentation)

No... they will only absorb enough oxygen oxygen to begin wall building.

if its a), doesn't this go against all previous knowledge and experience regarding the crabtree effect which causes anaerobic fermenation even in the presence of oxygen?

If you delivered the correct amount of oxygen to the starter, there will be no oxygen left in solution within 20 minutes. This assumes good yeast health, of course! I routinely measured this occurance while studing brewing microbiology at Siebel. It is a great indicator of yeast vitality.

Once budding has begun, there will be a small amount of fermentation going on, but the wort should be anaerobic at this point. Until critical population is reached and they stop reproducing, logarithmic fermentation will not begin.

Dr Strangebrew wrote:Eric, what do you mean by logarithmic fermentation in the above post?

Thank you,Nate

Logarithmic fermentation is when the yeast population attains their maximum ability to metabolize sugars. You can actually see this in a carboy or by observing your airlock bubbles. Visually it is when the surface of the wort is rocking quicky or, in an opaque fermenter, when the air bubbles are very fast... hardly a break between bubbles. It is also measurable by taking hydrometer or refractometer readings. When the daily readings are incrementing downwards evenly, they are in logarithmic fermentation. My average for ales strains is between 2.5 & 3.5 degrees plato and for lagers 1.5 & 2.5 degrees plato per day. This is strain, yeast viability and vitality, wort nutrition and temperature dependant.

I am curious to know an appropriate mathematical model for yeast growth i.e., yeast population as a function of time. Are you aware of any? I have a suspect, logistical growth, but I would like to know what you think. Allow me to elaborate. I believe that strain, temperature, wort nutrition... will affect the overall shape of the graph of some mathematical model. What is that model?

Labs do statistical analysis to acquire empirical data about yeast performance. I would predict that a "modeling" system would not really be of much value since attempting to predict how an actual, not lab, fermentation would go would have too wide of a standard deviation to provide useful info.

The authority on ultra scientific brewing science is the ASBC (American Society of Brewing Chemists). They are the brewing industry equivalent of The American Medical Association and just like AMA publishes JAMA, a cutting edge research digest, ASBC publishes a journal as well. You may wish to pose this question to them at http://www.asbcnet.org. But... if they have something you want to get and you aren't a member, the price is steep. If you do find something throught them, we may be able to work something out to get it to you at less cost as I am an ASBC member.

The best practice otherwise is to step the yeast culture up one day at a time to 100 ml, 200 ml, 400 ml, 800 ml and finally to 1,000 ml (5 total days of stepping) using a 5 deg. plato hopped wort (remember you want REPRODUCTION not fermentation, this is why the wort gravity is low.) While doing this, aerate 24 hours a day (builds strong cell walls/keeps yeast in a reproductive state) using the air pump/sterile filter method. For a 5 gallon batch, this should be adequate. If you do this, there is absolutely no need to aerate the wort.

Hi Eric. I am new to the board and have read the above and have a couple of questions.

A. I use a stir plate and I have understood that this provides oxygen as well or better than aeration with a stone. Do you have an opinion on this?

B. What is the advantage of stepping up for five days? I have been adding the yeast to my full amount - 1000 ml or 2000 ml. (then crash cooling to settle the yeast and using only the thick slurry)

C. If using the stepping up process as you describe, would there be a disadvantage to crash cooling and using only the slurry?

A. I use a stir plate and I have understood that this provides oxygen as well or better than aeration with a stone. Do you have an opinion on this?

Actually the only oxygen contribution would be from the headspace in the container. You should not be inviting air inward if it is sealed and airlocked. This is not enough air for yeast propagation. When you use an aquarium pump, filter and stone the air will only travel outward due to positive pressure which disallows air ingress protecting the wort from contamination. You should stir and aerate at the same time for maximum benefits.

B. What is the advantage of stepping up for five days? I have been adding the yeast to my full amount - 1000 ml or 2000 ml. (then crash cooling to settle the yeast and using only the thick slurry)

In proper propagation you are using a very low gravity wort. The idea is propagation, not fermentation. The step ups are timed so that as the sugar is depleted they do not go into fermentation but rather are hung in the reproductive state when you add additional wort. The cells are volume sensitive so when the addition of another dose of low sugar wort is made they reproduce in relation to the new volume. This continues to occur if done properly and the starter is not allowed to go anaerobic. To get the proper pitching volume takes an average of 4-5 days with this method. If you pitch this volume of starter into your full volume beer wort there will only be a short lag until the onset of fermentation while they acclimate themselves to the new volume.

By simply allowing a full volume starter wort to reproduce, ferment and settle as you described does not yield the same results, the worst of which is a greatly diminished cell count. If they flocculate it means you allowed them to go through reproduction, fermentation and then dormancy. This will create a significant lag time over the proper method and will lengthen the time required to ferment to your target gravity.

C. If using the stepping up process as you describe, would there be a disadvantage to crash cooling and using only the slurry?

Yes... this was partially answered above... by crash cooling you are forcing the cells into dormancy. This also reduces the viability or/and vitality of the cells as crashing them stresses them. The stress is additionally exacerbated since alcohol is present. The weaker cells with compromised cell walls can be destroyed in the presence of alcohol which is a solvent.

If possible, don't! The reason is that it is not the wort that needs the oxygen, it is the yeast. By oxgenating the wort instead of the yeast starter, it will cause an over production of cells due to the excessive oxygen presence. This then leads to the production of unwanted esters and higher alcohols that will compromise beer flavor.Eric

Eric,

This is a very interesting topic.

In regards to wort aeration, many texts on this topic have recommended otherwise. Even Dave Logsdon of Wyeast too advocated the aeration of wort in his Melbourne presentation last month.

However, I am more swayed towards yeast starter aeration rather than wort aeration for the reasons you have suggested, (and also because in an oxygen depleted environment yeast will begin anearobic fermentation rather than aerobic metabolism), but perhaps with one exception.......the brewing of high ester and phenol containing beers
such as Weizens. If aeration of weizen wort maintains yeast in a reproductive state than this will increase ester and phenol production. And perhas a short aeration would be more appropriate so as to reduce diacetyl. A diacetyl rest would also reduce this.

Contrary to the literature, I also favourite the pitching of yeast AFTER Kraussen in all non-weizen wort, for the reason that yeast after kraussen is no longer in exponential growth. After Kraussen, yeast will have primed themselves with glycogen stores and other reserves, ready for anaerobic fermentation. For weizen worts however, Kraussen yeast would be more ideal to enhance ester and phenol production.

"In regards to wort aeration, many texts on this topic have recommended otherwise. Even Dave Logsdon of Wyeast too advocated the aeration of wort in his Melbourne presentation last month."

I agree that there is contrary info out there... I was also taught this at both Weihenstephan & Siebel. I agree that wort should be aerated when the volume is over 1 bbl. But in homebrew volumes, aeration of the wort is not as critical. If you do aerate wort, don't do it with pure O2 unless you have the ability to measure dissolved oxgen in solution. Aerate with an aquarium pump, sterile air filter and a stainless stone.

"Contrary to the literature, I also favourite the pitching of yeast AFTER Kraussen in all non-weizen wort, for the reason that yeast after kraussen is no longer in exponential growth. After Kraussen, yeast will have primed themselves with glycogen stores and other reserves, ready for anaerobic fermentation."

Actually the yeast produce glycogen for dormancy not fermentation. If you let them go that far you will be introducing a lag. You want to pitch the yeast pre-krausen. If the yeast is krausening (is that a word?) it is in a fermentation stage not a reproductive stage and the solution would be anaerobic.

"For weizen worts however, Kraussen yeast would be more ideal to enhance ester and phenol production."

Actually for that yeast strain it would not matter as increasing it's ester & phenol producing ability is more temperature dependant than anything else. Volume of pitch can also change that profile somewhat.

I just found this topic, in fact, I just found BeerTools recently (I bought BeerTools Pro) after many years of being a ProMash guy. Anyway, very interesting subject to which I have a few questions after a quickie on my brew rig.

I have a HERMS set-up that I have been using for quite a while now. My normal procedure is to mash for 60 - 90 minutes (normally 60) while recircing the whole time. I am able to keep my mash temperatures pretty stable and reproducible from batch to batch. I typically mash at 1.25 qts/# and I have been using Five Stars 5.2 pH in my mash (not real certain if I am getting any benefit from 5.2 or not).

Questions:

1. Do you recommend 1.3 - 1.4 qts/# regardless of the method of mashing?
2. Are there any implications to the 20 minute mash using RIMS or HERMS or is it independent of mashing equipment?

Yeast Question:

1. Prowler 13 asked about using a stir plate. In reference to your answer could you not use a filter in your stopper while continuously stirring on the plate or is this not as sanitary as filter manufactures would lead us to believe?

2. I typically get yeast slurry from a local brewpub. Should this be pitched as is with no wort aeration?